1. Field of the Invention
The invention relates to communication networks, and more particularly to a mechanism for relaying messages via a wireless medium within a network environment.
2. Description of the Related Art
A wireless local area network (wireless LAN or WLAN) is a cellular network that facilitates communication via radio signals instead of wires. Wireless LANs are used increasingly in both home and corporate environments. Innovative ways to utilize WLAN technology are helping people to work and communicate more efficiently. The advantage of high mobility and the absence of cabling and other fixed infrastructure have proven to be a boon for many users. Wireless LAN users can use the same network applications they use on an Ethernet LAN. Wireless LAN adapter cards used on laptop and desktop systems, support the same protocols as Ethernet adapter cards. For most users, there is no noticeable functional difference between a wired Ethernet desktop computer and mobile WLAN workstation other than the added benefit of the ability to roam within the WLAN.
In 1997, the first wireless Ethernet standard, known simply as 802.11, was adopted and published by the IEEE. This unified standard provided several modes of operation and data rates up to a maximum two megabits per second (Mbps). Work soon began on improving the performance of 802.11. The eventual results were two new but incompatible versions of the standard, 802.11b and 802.11a. The “b” version operated in the same frequency range as the original 802.11, the 2.4 GHz Industrial-Scientific-Medical (ISM) band, but the “a” version ventured into the 5 GHz Unlicensed National Information Infrastructure (U-NII) band. 802.11b mandated complementary code keying (CCK) for rates of 5.5 and 11 Mbps, and included as an option Packet Binary Convolutional Coding (PBCC) for throughput rates of 5.5 and 11 Mbps, and additional range performance. 802.11a turned to another multi-carrier coding scheme, orthogonal Frequency Division Multiplexing (OFDM), and achieves data rates up to 54 Mbps. In June of 2003, IEEE announced its final approval of the IEEE 802.11g standard which adopted a hybrid solution that included the same OFDM coding and provided the same physical data rates of 802.11a. Nonetheless, 802.11g occupied the 2.4 GHz band of the original 802.11 standard.
The IEEE 802.11 standard is a member of the IEEE 802 family that specifies local area network technologies. 802.11 focuses on the lower two layers of the OSI model, the data link and physical layer. The simplest 802.11 networks consist of a group of stations that communicate with each other by creating a basic service set (BSS). There are two possible configurations of the BSS, Independent (IBSS) and infrastructure (known simply as BSS). An IBSS or ad hoc network consists of two or more wireless stations that communicate directly, peer-to-peer, without the services of an Access Point (AP). The IBSS is typically created for temporary communication between a few stations. The more common and reliable configuration is called infrastructure. In this configuration, each BSS has an AP, through which all communication is relayed. This can increase the coverage area since each station only needs to be within the range of a wireless AP. BSS and IBSS are certainly useful networks, but these independent topologies only facilitate communication between wireless stations. The most useful type of 802.11 configuration is the extended service set (ESS) created by linking BSSs with a backbone network. The backbone network is referred to as the distribution system medium and is typically wired Ethernet. Most wireless APs operate as bridges to the wired Ethernet LAN. In an ESS network, each wireless station appears as a normal Ethernet station to the rest of the nodes on the wired Ethernet LAN. The AP is responsible for bridging traffic to and from the wired LAN to the wireless LAN.
The IEEE 802.11 standard further defines the wireless distribution system (WDS) to wirelessly interconnect BSSs. Using WDS it is possible to wirelessly connect APs, and in doing so extend a wired infrastructure to locations where cabling is not possible or inefficient to implement. For example, WDS is a good solution to connect an office in a building across the street or connect a location in the manufacturing area where laying cable is complicated (and expensive). Unfortunately, IEEE 802.11 does not to date, specify the details of services provided by the WDS. At present, various manufacturers implement the WDS functionality in proprietary ways so only those APs made by a single manufacturer are able to be wirelessly interconnected via WDS, leading to less interoperability.
Accordingly, there is a need for an apparatus and method that can relay messages from a station to another BSS via a wireless medium. Specifically, it would be desirable to provide an AP with a mechanism for extension of an existing wired infrastructure without the use of WDS.